The PIAMA research project
The PIAMA-study is a large ongoing population-based birth cohort study with prenatal inclusion in 1996/96. The study was designed to investigate the influence of lifestyle and environment on the development of asthma, allergy and lung function. It therefore contains a detailed characterization of lifestyle and environmental exposures in all stages of childhood.
Study design and population
The study started with 3,963 newborns, who were born in 1996/97 after prenatal recruitment through prenatal clinics in the northern, middle and southwestern part of the Netherlands. The figure below shows the places in which the participating prenatal clinics were located (fig. 1a) and the places where the participants lived in 2019 (fig. 1b).
After inclusion, allergic and non-allergic mothers were identified through a validated screening questionnaire. Pregnant women identified as allergic were primarily allocated to an intervention study with a random subset allocated to a “natural history study”. The intervention involved the use of mite-impermeable mattress and pillow covers on the children’s and parents’ beds. Non-allergic pregnant women were invited to participate in a “natural history” study arm.
The intervention part and the natural history part were integrated into one study: the PIAMA birth cohort study with two main aims:
- to investigate the effect of mite-allergen avoidance on the incidence of asthma and allergy in childhood (Intervention study); and
- to investigate lifestyle and environmental (indoor and outdoor) risk factors for childhood asthma and allergy (Natural History study).
The evaluation of the effectiveness of the mattress covers in terms of reducing allergen exposure preventing asthma and allergies at age 8 years, showed that the covers were successful in reducing exposure to house dust mite Der f1, but not Der p1, and did not succeed in preventing asthma and allergy outcomes. More information on the intervention study, see pubMed 22023655.
This is consistent with findings of other prospective birth cohort studies investigating the independent effects of HDM allergen reduction on the development of asthma and allergies, but may partly be attributable to the fact that the PIAMA intervention study by coincidence recruited its participants in years with two consecutive very cold winters, which significantly reduced mite allergens in all arms of the study, so that the effect of the intervention was considerably smaller than it could have been.
At the start of the study, the length of follow-up was planned to be 8 years to allow sufficient time for allergic sensitization and symptoms to develop. The study was highly successful both in terms of follow-up rates (Figure 2) and in terms of the wealth of data obtained.
Figure 2. Response per follow up.
These success factors in combination with new research questions that came up during the course of the study were reason for the investigators to extend the follow-up beyond the age of 8 years and also to broaden the scope of the health outcomes investigated to cardiometabolic health outcomes. Three years after the originally planned 8 years of follow-up had been completed, the remaining participants were invited to participate in additional waves of data collection at the ages of 11, 14, 17, 20 years and 23-25 years (Figure 3).